Which of the following represents s - s, s - p and p - p overlap respectively?
I, III, II
Let's see, what will be s - s, s - p and p - p overlap.
s-s overlap → Overlap of two half filled s-orbitals along the inter-nuclear axis.
s-p overlap → Overlap between half-filled p-orbitals of one atom and half-filled s-orbitals of another atom.
p-p overlap → Overlap between half-filled p-orbitals of the two approaching atoms.
Therefore, the correct order is
I ⇒ s−s overlap,II ⇒ p−p overlap and III ⇒ s−p overlap